STABLY STRATIFIED FLOWS IN METEOROLOGY

It is generally believed by those undertaking research in the fundamen tal aspects of geophysical fluid dynamics and meteorology that their r esults contribute to the improvements to numerical weather prediction and in practical weather forecasting. However, the techniques whereby the appropriate research results are selected and incorporated into th e numerical models are not widely known, particularly the methods for representing the phenomena whose horizontal scale is less than that of the grid boxes.(say, 50 km). Some accounts of numerical weather predi ction imply that the representation of subgrid-scale phenomena is form ally similar to classical physics. In fact, atmospheric motions on the se scales are not like molecular motions in an ideal gas, but show con siderable structure, approximating to combinations of various idealize d states. Great skill and experience in this specialized activity has been applied to deciding on these states, finding physical criteria fo r defining them and then modelling the relevant phenomena occurring on this scale. In this paper, we focus on a restricted range of phenomen a associated with stably stratified flows, notably mountain waves, con vection and clouds, and boundary layer phenomena. This category provid es many examples of structures which need to be considered in detail t o reconstruct the large-scale picture accurately, as well as in local forecasting.